As for a lateral semiconductor device in which current flows in the parallel direction to a surface of a semiconductor layer, an electrode provided on a surface of the semiconductor layer and a back electrode provided on a back surface of the semiconductor layer are electrically connected using a via hole. Thereby, a surface side electrode is grounded and operation of the semiconductor device is stabilized. Since a metal layer which is simultaneously formed with an ohmic electrode is generally used as the surface side electrode, the surface side electrode consists of an alloy layer containing gold germanium (AuGe), nickel (Ni) and gold (Au), and a reaction layer which is formed by reaction of the alloy layer and the semiconductor layer. A hole of the via hole is formed by etching the semiconductor layer selectively using an RIE (Reactive Ion Etching) method, for example. Etching gas contains chlorine, for example.
The surface side electrode may deform with the heat at the time of mounting the semiconductor device on a package or a mounting board, and thereby a contact between the surface side electrode and the back electrode may become unstable.
The embodiment supplies a reliable semiconductor device in which a connection between a surface side electrode and a back electrode through a via hole is stable.